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**Harvard**

van Wyk, F., Highcock, E., Field, A., Roach, C., Schekochihin, A., Parra, F. och Dorland, W. (2017) *Ion-scale turbulence in MAST: anomalous transport, subcritical transitions, and comparison to BES measurements*.

** BibTeX **

@article{

van Wyk2017,

author={van Wyk, F. and Highcock, Edmund and Field, A. R. and Roach, C. M. and Schekochihin, A. A. and Parra, F. I. and Dorland, W.},

title={Ion-scale turbulence in MAST: anomalous transport, subcritical transitions, and comparison to BES measurements},

journal={Plasma Physics and Controlled Fusion},

issn={0741-3335},

volume={59},

issue={11},

pages={114003},

abstract={We investigate the effect of varying the ion temperature gradient (ITG) and toroidal equilibrium scale sheared flow on ion-scale turbulence in the outer core of MAST by means of local gyrokinetic simulations. We show that nonlinear simulations reproduce the experimental ion heat flux and that the experimentally measured values of the ITG and the flow shear lie close to the turbulence threshold. We demonstrate that the system is subcritical in the presence of flow shear, i.e., the system is formally stable to small perturbations, but transitions to a turbulent state given a large enough initial perturbation. We propose that the transition to subcritical turbulence occurs via an intermediate state dominated by low number of coherent long-lived structures, close to threshold, which increase in number as the system is taken away from the threshold into the more strongly turbulent regime, until they fill the domain and a more conventional turbulence emerges. We show that the properties of turbulence are effectively functions of the distance to threshold, as quantified by the ion heat flux. We make quantitative comparisons of correlation lengths, times, and amplitudes between our simulations and experimental measurements using the MAST BES diagnostic. We find reasonable agreement of the correlation properties, most notably of the correlation time, for which significant discrepancies were found in previous numerical studies of MAST turbulence.},

year={2017},

keywords={gyrokinetic simulations, flow shear, ion temperature gradient, subcritical turbulence},

}

** RefWorks **

RT Journal Article

SR Electronic

ID 252452

A1 van Wyk, F.

A1 Highcock, Edmund

A1 Field, A. R.

A1 Roach, C. M.

A1 Schekochihin, A. A.

A1 Parra, F. I.

A1 Dorland, W.

T1 Ion-scale turbulence in MAST: anomalous transport, subcritical transitions, and comparison to BES measurements

YR 2017

JF Plasma Physics and Controlled Fusion

SN 0741-3335

VO 59

IS 11

AB We investigate the effect of varying the ion temperature gradient (ITG) and toroidal equilibrium scale sheared flow on ion-scale turbulence in the outer core of MAST by means of local gyrokinetic simulations. We show that nonlinear simulations reproduce the experimental ion heat flux and that the experimentally measured values of the ITG and the flow shear lie close to the turbulence threshold. We demonstrate that the system is subcritical in the presence of flow shear, i.e., the system is formally stable to small perturbations, but transitions to a turbulent state given a large enough initial perturbation. We propose that the transition to subcritical turbulence occurs via an intermediate state dominated by low number of coherent long-lived structures, close to threshold, which increase in number as the system is taken away from the threshold into the more strongly turbulent regime, until they fill the domain and a more conventional turbulence emerges. We show that the properties of turbulence are effectively functions of the distance to threshold, as quantified by the ion heat flux. We make quantitative comparisons of correlation lengths, times, and amplitudes between our simulations and experimental measurements using the MAST BES diagnostic. We find reasonable agreement of the correlation properties, most notably of the correlation time, for which significant discrepancies were found in previous numerical studies of MAST turbulence.

LA eng

DO 10.1088/1361-6587/aa8484

LK http://dx.doi.org/10.1088/1361-6587/aa8484

OL 30